1. Field of the Invention
The present invention relates to a control valve and, more particularly to a structure of a vibration-proof spring suitable in preventing the vibration of an actuating section of the control valve.
2. Description of the Related Art
A refrigeration cycle in an automotive air conditioner is generally configured such that the refrigeration cycle includes a compressor, a condenser, a receiver, an expansion valve, and an evaporator. The compressor compresses a circulating refrigerant. The condenser condenses the compressed refrigerant. The receiver separates the condensed refrigerant into a gas and a liquid. The expansion valve throttles and expands the separated liquid refrigerant and delivers it by turning it into a spray. Then the evaporator evaporates the misty refrigerant and thereby cools the air inside a vehicle by the evaporative latent heat. Used as the expansion valve is a thermostatic expansion valve that senses the temperature and pressure of refrigerant at an outlet side of the evaporator such that, for example, the refrigerant led out from the evaporator has a predetermined degree of superheat and that controls the flow rate of refrigerant delivered to the evaporator by opening and closing a valve section.
This expansion valve includes a body formed with a first passage for passing the refrigerant flowing from the receiver to the evaporator and a second passage for passing the refrigerant returned from the evaporator and then supplying the refrigerant to the compressor. A valve hole is formed midway in the first passage. Provided is a valve element that closes and opens a valve section by touching and leaving the valve hole, respectively. The valve element, which moves toward and away from the valve hole, regulates the flow rate of refrigerant flowing toward the evaporator. Also provided is a power element that senses the temperature and pressure of refrigerant flowing through the second passage and controls the valve opening degree of the valve section. The drive force of the power element is transmitted to the valve element by way of an elongated shaft. One end side of the shaft is connected to the power element across the second passage. The other end thereof is connected to the valve element such that the shaft passes through an insertion hole and a valve hole formed in a partition wall provided between the first passage and the second passage.
In such an expansion valve, the pressure may fluctuate in an upstream side of the valve section where, for example, a high-temperature refrigerant is introduced. If this problem of fluctuation is left unattended, the valve element may vibrate and generate noise. The following method is available to alleviate this problem. That is, a mounting hole formed coaxially with the insertion hole is formed in the partition wall and then a cylindrically-shaped vibration-proof spring is provided in the mounting hole; this vibration-proof spring biases the shaft radially inward thereof so as to develop a sliding friction (resistance) and, as a result, the valve element does not respond sensitively to the fluctuation in pressure (see Reference (1) in the following Related Art List, for instance).